100 Gbit/s V-band Transmission Enabled by Coherent Radio-over-Fiber System with IF-OFDM Envelope Detection and SSBI Suppression

In this paper, the successful demonstration of a 100 Gbit/s wireless backhaul link in the V-band is reported for the first time. The proposed system has potential for real-world deployment since it exploits the contiguous unlicensed spectrum of 14 GHz in the 60 GHz V-band between 57 GHz and 71 GHz. Optical baseband modulation and free-running lasers for photonic up-conversion are employed in the wireless transmitter and simple Schottky-barrier diodes (SBD) for envelope detection are used in the wireless receiver. This combination makes perfect use of the scalability of photonic technology with respect to modulation bandwidth while being robust against phase-noise and frequency drifts at the same time. By utilizing a dual-polarization (DP) 16-QAM IF-OFDM signal no local oscillator is required at the wireless receiver. To achieve the required high spectral efficiency for 100 Gbit/s wireless transmission in the available spectrum as well as a low baseband bandwidth, signal-signal beat interference (SSBI) has been substantially reduced. This is attained by analyzing non-linearities in the wireless transmitter for identifying and setting the optimum power relation between the IF carrier and the OFDM signal. Experimentally, we report 100 Gbit/s wireless V-band transmission using a DP IF-OFDM 16-QAM modulation over 1 m distenace. The achieved overall BER before FEC and overall wireless spectral efficiency are $2.4.10^{-3}$, and $\sim 7$ bit/s/Hz, respectively. For simplicity, experiments were carried out in a laboratory environment. By using commercially available high-gain antennas and RF power amplifiers, the link budget could be increased by about 7080 dB which would lead to longer wireless distances in the range of several 100 meters up to kilometers.